Laboratory Studies

Immunostaining with vimentin, alpha smooth muscle actin, muscle actin, and desmin are helpful in distinguishing the tumors in the differential diagnosis of desmoid tumors.

APC germline mutations in apparently sporadic desmoid tumor patients who have no clinical or familial signs of familial adenomatous polyposis (FAP) but have a family history of colorectal carcinoma in at least one family member were evaluated by Brueckl et al
[3] in 2005. They reported that patients with sporadic desmoid tumors and no clinical or laboratory signs of FAP may not need to be routinely tested for germline mutations of the APC gene. However, performing an APC mutational analysis instead of other tests (eg, esophagogastroduodenoscopy, complete colonoscopy) may be a more time- and cost-effective plan.

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Imaging Studies

CT scanning and MRI are used for the diagnosis and follow-up of desmoid tumors. They can help determine the extent of the tumor and its relationship to nearby structures, especially prior to surgical removal. MRI is superior to CT scanning in defining the pattern and the extent of involvement as well as in determining if recurrence has occurred after surgery.

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Procedures

The preferred diagnostic test is biopsy of the tumor. A fine-needle aspiration biopsy specimen may be considered.
[33]

Electron microscopy may be performed. On electron microscopic examination, the spindle cells of desmoid tumors appear to be myofibroblasts. This finding is thought to represent an abnormal proliferation of myofibroblasts, which normally disappear gradually during the later stages of wound healing.

The aforementioned features are in contrast to those in a fibrosarcoma, which has greater mitotic activity, an increased nuclear-to-cytoplasm ratio, greater vascularity, less collagen production, and a paucity of immune cells.
[9]

Bland fibrocytic cells of a desmoid tumor growing in a haphazard-to-storiform manner and producing collagen (hematoxylin-eosin, original magnification X100).

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Contributor Information and Disclosures

Author

Robert A Schwartz, MD, MPH Professor and Head of Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, Rutgers New Jersey Medical School; Visiting Professor, Rutgers University School of Public Affairs and Administration

Neil Shear, MD Professor and Chief of Dermatology, Professor of Medicine, Pediatrics and Pharmacology, University of Toronto Faculty of Medicine; Head of Dermatology, Sunnybrook Women's College Health Sciences Center and Women's College Hospital, Canada